This invention relates to a bobbin doffing and donning method and apparatus, applicable to a spinning machine, of the type which comprises a single conveyor and a refuge support, either full bobbins or empty bobbins being temporarily placed on the refuge support on the way thereof from the spindles of the spinning machine to the conveyor or vice versa.
In the above-mentioned type of conventional doffing apparatus, a doffing bar with a number of bobbin holders is generally included so that all the full bobbins on the spindles on each side of the spinning machine are doffed simultaneously by moving the doffing bar in predetermined sequence with respect to the spindles. Typically, such a motion of the doffing bar includes swinging, upward and downward movement of the same. Also, the swinging movement is generally effected by causing the doffing bar to turn about a shaft extending therealong by means of a piston and cylinder assembly.
In order to temporarily place the empty bobbins on the refuge support positioned between the row of spindles and the conveyor, the doffing bar has to be temporarily maintained in an intermediately inclined condition, under which the bobbin holders supported by the doffing bar with the empty bobbins can place the latter on the refuge support. For this purpose, the doffing apparatus is provided with means associated with the piston and cylinder assembly for restraining the doffing bar in the intermediately inclined condition.
However, since the piston and cylinder assembly has essentially no function of allowing the piston itself to temporarily stop at any intermediate position between the ends of a stroke thereof, the restraining means including a stop to constrain the piston at its intermediate position is necessarily subject to the force produced by a pressure applied on the piston. Therefore, in order to release the stop of the restraining means from the piston constraining position thereof against the pressure in the cylinder, considerable power is required to operate the restraining means, resulting in an increased capacity of the restraining means. Moreover, upon release of the restraining means, the restoration of the movement of the doffing bar to another condition by the piston and cylinder assembly causes an impact on the doffing bar and the associated parts. This results in the prevention of a smooth doffing operation.
it is therefore a principal object of this invention to provide a bobbin doffing and donning method and apparatus, which requires much less power to release the means for restraining a doffing bar from an operative position, and which ensures a stable and smooth doffing operation.